Improvement in cut-off valve-gears



UNITED STATES PATENT FETE; f t

ALEXANDER W. FOSTER, JR., 0F PITTSBURG, PENNSYLVANIA".l 1 i IMPROVEMENTIN CUT-oFF VALVE;(TEARS. 7/

Specification forming part of Letters Patent N0. 51,821, dated January2, 1866.

To all whom it may concern:

Be it known that I, ALEXANDER W. Fos- TER, J r., of Pittsburg, in thelcounty of Allegheny and State of Pennsylvania, have invented a new andImproved Adjustable Out- Of'; and I do hereby declare that the followingis a full, clear, and exact description thereof,

- which will enable those skilled in the art to make and use the same,reference being had to the accompanying drawings, forming part of thisspecitication, in Which-'- Figure l represents a front elevation of thisinvention. Fig. 2 is a side elevation of the same.

Similar letters of reference indicate like parts.

vkept open for a shorter time than it is when the speed of the engineslacks off and the balls of the governor sink down. The several camswhich form the combination-cam are made V-shaped, and they operate, incombination with a V-shaped friction-roller at the end of thevalve-stem,in such a manner that the governor is prevented from movingthe cam While the valve is being seated, and the length 0i' the severalcams is so adjusted in relation to each other that each cam cuts oft' ata certain constant or regular percentage on the one immediatelypreceding, thus differing from ordinary cut-offs, which cut of at equalintervals on the stroke of the piston.

A represents the cut-off or throttle-valve of a steam-engine, which isopened and closed by the action of a combination cam or drum, B. Thisdrum slides back and forth on its axis C, and it is to be connected withthe governor in such a manner that itis moved on its axis in thedirection ot' the arrow (marked near it in Fig. 2) when the speed of theengine increases and the balls y out, and in the direction opposite tosaid arrow when the speed of the engine decreases and the balls of thegovernor shut down.

The cam or drum B is composed of a series of cams, l 2 3 9 l0, whichdecrease in length, and as said drum rotates with the axis C one of thecams, 1. 2 3, te., acts on the frictionroller a in the end of thevalve-stem and raises the valve, keeping it open for a longer or shorterperiod, according to the length ot' the cam acting on the roller. Thecam lis the longest of the series, and i the drum B is brought in such aposition that this cam acts on the valve said valve is kept open duringthe entire stroke of the piston. The next succeeding cam, 2, is somewhatshorter than the cam l, &c., down to the cam l0, which is the shortest,and keeps the valve open only for a very small portion of the stroke.The length of the cams decreases according to a certain rule, so thateach cam cuts oft' at a certain constant or regular percentage on theone next preceding. For instance, suppose atWo-foot enginecam No. 10 tobe live inches on the stroke, by adding twenty per cent. We have No. 9at six inches, and twenty per cent. on this for N o. 8 at seven andtwo-tenths inches; for No. 7 add twenty per cent. on the last giveseight and sixty-four one-hundredths inches; for N o. 6` we have nine andthirty-seven one-hundredths; for No. 5 we have eleven and fourteenone-hundredths; for N o. 4 we have thirteen and thirtysevenone-hundredths; for No. 3, sixteen and four one-hundredths; for No. 2,nineteen and twenty-tive one-hundredths, and for N o. 1 we have twenty-three and ten lone-hundredths inches. By this arrangementthe speed ofthe engine is rendered more regular and more uniform than by theordinary cut-oft' arrangements, which cut oft' at equal intervals on thestroke ofthe piston.

The working-faces of the cams l 2 3, &c., form V-shaped grooves, and theface of the friction-roller t is formed to correspond to said grooves,so that while the valve is being seated-that is to say, during the timethe roller a runs in the V-shaped groove of one of the cams-the drum Bcannot be shifted on the axis C bythe action of the governor. By thisarrangement violent iluctuations ofthe governor are prevented and thespeed of the engine is gradually brought to the desired point.

I am aware thatcut-oft's have been used analogous in principle to mine,but having a single oblique-faced cam instead of the series of erate in`combination with the valve A, substantially as and for the purposedescribed.

2'. Providing the Working-faces of the cams l 2 3 10 with V`shapedgrooves to operate in combination with the V-shaped roller al on thevalve-spindle, substantially as and for the purpose set forth.

ALEXANDER W. FOSTER, JR.

Witnesses: A. W. FOSTER,

DOUGALD MUNN.

